The Cosmic Spider-Man Saga
Furious over his defeat at the hands of Thor and The Avengers during Acts of Vengeance; Loki, the Asgardian God of Mischeif, used his dark magics to fuse three Project: NIMROD prototype Sentinels into the ultimate weapon, a perfect hybrid born from the mingling of magic and science.
In addition, Loki gave The Tri-Sentinel numerous mystical upgrades and replaced its programming with "The Loki Prime Directive" dictating that the Tri-Sentinel proceed to The Amity Point Nuclear Power Plant and Destroy it, this would result in the annihilation of Manhattan.
However, the coming of the Tri-Sentinel had been foreseen by the Enigma Force, who empowered the street-wise superhero called Spider-Man with the cosmic might of Captain Universe, whose true power had been locked away due to interference from a machine designed to contain extra-dimensional energy sources very much like The Uni-Power.
Although, the interference was eventually dealt with when Sebastian Shaw tried to usurp Spider-Man's new mysterious powers via the use of the very same machine that had caused the problem in the first place and by doing so unlocked the rest of Captain Universe's powers allowing Spider-Man access to more power as well as The Uni-Power's cosmic awareness.
Arriving just in the nick of time, Spider-Man attacked the Tri-Sentinel and fought a desperate battle to keep it from accomplishing its mission. Sebastian Shaw, (who had had the foresight of installing a safety measure into the logic boards of All three prototypes prior to their merger), sent out the signal required to activate the safety measure and effectively shut The Tri-Sentinel down.
The program had been designed specifically for the purpose of stopping the Sentinels if they went rogue, once activated it would make the Sentinels think that because they inherited most of their traits from the Mark I Sentinels that they themselves (being merged) were Mutants whom they were programmed to destroy. In theory, any rogue Sentinel receiving the signal would destroy itself.
However, The Tri-Sentinel managed to override the program thanks to its triple-logic boards and mystical programming and started swinging its fists on one of the containment towers. But thanks to the iron will of Spider-Man and the unfathomable cosmic might of Captain Universe, the Tri-Sentinel was destroyed.
The Life Foundation's Blunder
Sometime later, The Life Foundation gathered up the remains of The Tri-Sentinel from Amity Point and rebuilt it, hoping to use it as a weapon against Mutantkind, but upon activating it the Tri-Sentinel's new programming was overwritten by "The Loki Prime Directive" and so, the Tri-Sentinel set out to complete its original mission. Without the Uni-Power at his disposal anymore, Spider-Man called Richard Rider a.k.a. Nova, for help and together they managed to destroy The Tri-Sentinel once and for all.